Field of the Invention
This invention relates to a combination scale configured to weigh a predetermined quantity of articles, such as various kinds of foodstuffs, more particularly to a combination scale to which thermal management solutions have been applied.
Conventionally, a combination scale is structurally characterized as described below. Articles to be weighed supplied to the combination scale are radially distributed by a distribution feeder. The distributed articles are delivered by a plurality of linear feeders linearly outward by way of vibrations and thrown in a plurality of feeding hoppers facing delivery ends of the linear feeders. The feeding hoppers open their gates to feed the articles into a plurality of weigh hoppers disposed below. The combination scale variously combines the articles in the weigh hoppers to select a combination of weigh hoppers in which a total weight value of the articles fails within a predetermined weight range. Then, the combination scale opens the gates of the selectively combined weight hoppers to discharge the articles via, for example, collecting chutes, into a packaging machine installed down below.
There is a central cabinet having a hollow interior at the center of the combination scale. In the interior of the cabinet are housed vibration exciters that vibrate the respective feeders, driving units that open and close the gates of the hoppers, and weighing units including weight sensors that detect weights of the articles thrown in the weigh hoppers.
The central, cabinet is a closed type container to block any foreign matter or articles to be weighed that might otherwise enter therein. In the closed central cabinet, its internal temperature is often elevated by heat generated from, for example, the driving units, or by heat transmitted from hot articles to be weighed. These thermal impacts elevate the internal temperature of the central cabinet, adversely affecting the devices housed in the central cabinet, typically the weight sensors. This may be a problem in that weight values become unstable.
As possible solutions to such a problem, the central cabinet may be ventilated, to lower its temperature inside as described in the patent document 1 or 2, or the central cabinet may be directly cooled by a Peltier device as described in the patent document 3. The cited documents 1 to 3 are listed below.    Patent Document 1: Japanese Laid-Open Patent Application No. H06-317454    Patent Document 2: Japanese Laid-Open Patent Application No. 2001-255199    Patent Document 3: Japanese Laid-Open Patent Application No. 2014-134423
In the patent documents 1 and 2, since the electrically-driven fans are used for ventilation, fan motors driving the fans becomes heat sources and additionally, in the case of waterproof combination scales, integral waterproofing is required tor a wiring system of the fan motors.
In the scale described in the patent document 3, the location of the Peltier device and its vicinity may be efficiently cooled. Yet, hot air is likely to rise and rest in an upper part of the cabinet interior, and this scale farther needs a fan for ventilation in order to cool the entire cabinet interior, which invites cost increase.
The invention was accomplished to solve these conventional problems. The invention provides a combination scale wherein a cabinet may be efficiently ventilated to cool its interior in the absence of any fans to enable a weighing performance substantially heat-unaffected and thereby improved in accuracy.